Checking battery level in Java ME

Article Metadata

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Code Example

Source file: Media:BatteryLevelSource.zip

Installation file: Media:BatteryLevelBinaries.zip

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Tested with

Devices(s): Nokia E70, Nokia N78, Nokia 701

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Compatibility

Platform(s): S60 3rd Edition, S60 3rd Edition, FP1, S60 3rd Edition, FP2

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Article

Keywords: java.lang.System.getProperty, com.nokia.mid.batterylevel

Created: vltsoy (27 Nov 2008)

Last edited: mtilli (13 Aug 2012)

Overview

This code snippet demonstrates how to retrieve the current battery level.

The application retrieves the system property com.nokia.mid.batterylevel which contains the current battery level (in per cent) and displays it.

Note that in Series 40 platform only signed MIDlets under operator domain can retrieve this information.

Source file: BatteryLevel.java

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.StringItem;
import javax.microedition.midlet.MIDlet;
 
 
public class BatteryLevel extends MIDlet implements CommandListener{
 
    private Display display;
    private Form form;
    private Command exitCommand;
    private Command refreshCommand;
    private StringItem level;
 
 
    /**
     * Constructor. Constructs the object and initializes displayables.
     */
    public BatteryLevel() {
        form = new Form("Battery level.");
 
        exitCommand = new Command("Exit", Command.EXIT, 2);
        refreshCommand = new Command("Refresh", Command.OK, 1);
 
        level = new StringItem("", "");
        form.append(level);
 
        form.addCommand(exitCommand);
        form.addCommand(refreshCommand);
        form.setCommandListener(this);
 
        display = Display.getDisplay(this);
        display.setCurrent(form);
 
        checkBatteryLevel();
    }
 
    /**
     * From MIDlet.
     * Called when the MIDlet is started.
     */
    public void startApp() {
        // No implementation required.
    }
 
    /**
     * From MIDlet.
     * Called to signal the MIDlet to enter the Paused state.
     */
    public void pauseApp() {
        // No implementation required.
    }
 
    /**
     * From MIDlet.
     * Called to signal the MIDlet to terminate.
     * @param unconditional whether the MIDlet has to be unconditionally
     * terminated
     */
    public void destroyApp(boolean unconditional) {
        // No implementation required
    }
 
    /**
     * From CommandListener.
     * Called by the system to indicate that a command has been invoked on a
     * particular displayable.
     * @param cmd the command that was invoked
     * @param displayable the displayable where the command was invoked
     */
    public void commandAction(Command c, Displayable d) {
        if (c == refreshCommand) {
            checkBatteryLevel();
        } else if (c == exitCommand) {
            notifyDestroyed();
        }
    }
 
    /**
     * Called to read current battery level.
     */
    private void checkBatteryLevel() {
        String property = System.getProperty("com.nokia.mid.batterylevel");
        if (property == null) {
            level.setLabel("Error:\n");
            level.setText("Unable to retrieve current battery level.\n" +
                          "It's only available for signed midlets " +
                          "under operator domain.");
        } else {
        level.setLabel("Current battery level:");
        level.setText("\n"+property+"%");
        }
    }
}

Postconditions

This code displays the current battery level in per cent.

Supplementary material

The example project and binary files are available for download at Media:BatteryLevelSource.zip and Media:BatteryLevelBinaries.zip.